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Essentially just #645 which fixes compilation on OS X

Fixed memory leak reported in #633

Add -fpermissive plus some other minor things

• Multithreaded building by @novoselrok
• Misc updates of README to link to Ruby bindings and clean up docs
• Better tree splitting, try multiple times ot find more balanced ones
• Fix building on disk and saving large files for Windows
• Misc compilation warnings cleanup

• mostly fixing windows issues with large files
• some error message improvements as well
• doing more stack allocations instead of heap
• fixes to a few tests that were failing on other platforms

Something is busted with version 1.16.1 where I think I must have accidentally uploaded it a long time ago.

Bumping straight to 1.16.2

This is same content as 1.16.1

Mostly minor things to catch user errors and/or explain things better. No functionality change really, except preventing some questionable usage patterns that lead to lots of complexity.

#430 – AVX issues in certain GCC version #427 – Prevent saving an index that hasn't been built #425 – Prevent building an index that has already been built #426 – Handle lseek failures #419 – ftruncate issues #410 – swig update #405 – Use std::sort

The remaining changes were to documentation/test and don't change any functionality

• Fix #379 error handling in save()
• Fix compile issue in linux
• Fix popcount #366
• Some more misc